Authors: J.R. White1, N. Khalid2, M.L. Tao3, L.J. Pierce4, A. DeRobertis5, C. Crozier2, J.B. Owen2 and J.F. Wilson1
Institution: 1Medical College of Wisconsin, Milwaukee, WI 2American College of Radiology, Philadelphia, PA 3Epic Care, Orinda, CA 4University of Michigan Medical School, Ann Arbor, MI 5Massachusetts General Hospital, Boston, MA
Radiotherapy techniques in the treatment of breast cancer are continuing to evolve
The American College of Radiology (ACR), Quality Research in Radiation Oncology (QRRO) periodically surveys US radiation facilities regarding use of various technologies and techniques employed for radiation planning and delivery.
Prior survey QRRO results in 1999 found CT based planning to be employed in 22% of cases
In 2007, the QRRO survey again evaluated the quality of breast cancer treatment planning and delivery and documented integration of newer radiation methods since its last survey in 1999. These results are presented here.
Materials and Methods
QRRO used a two-staged stratified random sample to perform a national survey of the treatment of operable breast cancer patients in 2007 in the USA
There were 1879 radiation facilities nationally in 4 strata;126 institutions were randomly selected and invited; 42 accepted the survey
Each facility provided their list of patients treated and this yielded 412 cases from 42 randomly institutions.
Eligible cases included: treatment with XRT in 2007 for operable invasive breast cancer (stages I, II, or IIIA) treated with breast conservative surgery (CS) or mastectomy (M)
The survey gathered demographic data, information on contoured volumes, and dose-volume histogram (DVH) data
Of the 412 cases, 137 cases were from academic medical centers
Out of 412 cases 52% were pathologically stage I, 25% Stage IIA, 9% Stage IIB, and 12%, Stage IIIA.
Ethnicity: most women were Caucasian
¾ of patients had hormone receptor positive disease
Surgical treatment was CS in most (84%) and M for 16%.
Sentinel node biopsy was performed for 72.6%, axillary node dissection (AND) in 46%.
One hundred twenty patients (29%) had positive axillary nodes.
Nodal status was N0 in 62%, N0 IHC+ 8.5%, N1 mic 4%, N1 16%, N2 9.3%.
Radiation (RT) consisted of partial breast irradiation (PBI) in 4.8%, whole breast alone 68%, whole breast and nodes 10.7%, and postmastectomy 16.0%
The mean breast and chest wall dose was 48 Gy
The mean boost dose was 13 Gy
For nodal treatment, the areas treated were supraclavicular (SCL) and axillary (AX) apex in 84.3%, SCL and full AX 13.7%, separate AX field 29.4%, and IMN 26.5%.
CT planning scans were done for 97%.
After CS, the isodose planning method employed was central plane 1.5%, multiple axial planes 2.1%, 3DCRT 79.2%, IMRT 16%
After M, the isodose planning method employed was central plane 0%, multiple axial planes 7.5%, 3DCRT 82%, IMRT 10.5%.
Following CS, contoured CT volumes were contoured for a lumpectomy CTV/PTV for 96%, breast 92%, lung 94%, and heart 59.6%
DVHs were analyzed for lumpectomy CTV/PTV in 70%, breast 20%, lung 78% and heart 51%.
Following M, CT volumes were contoured for chest wall 95%, lung 95.5%, and heart 63.6% ; DVHs were analyzed for chest wall in 21%, lung 79% and heart 48.5%.
Multi-leaf collimation (MLC) was the most common form of beam modifier used, followed by physical (30%) then dynamic wedges (19%).
For the 27 PBI cases, 10 were treated brachytherapy, seven were treated with 3DCRT
100% had a CT based plan and 78% had a DVH present.
All met requirements for the prescription dose to cover 90% of PTV
Skin toxicity was assessed weekly in 89%
dry desquamation occurred in 38%; moist 13%
57.8% had either dry or moist desquamation; there was more moist desquamation in 3D than IMRT based plans
The rate for any desquamation for 3DCRT methods was 52%, 52% for IMRT, and all other 71% (p = 0.125).
Breast pain occurred in 40%.
IMRT is more common in small non academic centers in the Northeast USA
ACR QRRO documents change in the technical delivery of RT for breast cancer as of 2007 compared to 1999, when CT planning and conformal methods were uncommonly used.
3DCRT/IMRT methods are now predominant
Contoured CT volumes are normally done, but there is less documentation of DVH for plan analysis than would be predicted
Nearly all breast cancer treatment now is CT based. This allows more accurate assessment of dose distribution than 2D planning. It is unclear why there were situations where contours were done but corresponding DVHs were not, but this may be a reflection of the continued use of traditional 2D parameters in 3D planning (such as measuring the number of centimeters of lung in a tangent field or prescribing a SC field to a depth of 3 cm).
3D CRT is the most common technique employed, but IMRT and PBI use is increasing.
While the use of IMRT did not appear to have a significant effect on acute skin toxicity, the impact of use of IMRT on other clinical outcomes and its impact on dosimetric parameters were not assessed.
The use of IMRT also varies depending on facility and geography. The lower use of IMRT within academic practices as compared to small private practices suggests that economic considerations may influence decisions about radiation technique, but a more detailed questionnaire specifically asking what factors play into the use of IMRT would be useful in drawing more firm conclusions.